Add support for an embedded symbol table

6 files changed, 169 insertions, 4 deletions

diff --git a/Kconfig b/Kconfig
index 911fd274..479ab45a 100644
--- a/Kconfig
+++ b/Kconfig
@@ -47,6 +47,18 @@ config ASSERT
 	---help---
 	  Enable assert() code generation.
 
+config SYMTAB
+	bool "Build symbol table"
+	default y
+	---help---
+	  Build and embed a symbol table in the kernel.
+
+	  This option allows the kernel to perform symbolic address
+	  resolutions which are very convenient for debugging, at the
+	  cost of additional data memory.
+
+	  If unsure, enable.
+
 endmenu
 
 source "arch/$ARCH/Kconfig"
diff --git a/Makefile b/Makefile
index 05e8228a..b5f9410a 100644
--- a/Makefile
+++ b/Makefile
@@ -85,10 +85,19 @@ define xbuild_link
 		$(COMPILE) -o $@ $(1) $(XBUILD_LDFLAGS)
 endef
 
+XBUILD_GEN_SYMTAB = $(SRCDIR)/tools/gen_symtab.py
+XBUILD_GEN_SYMTAB_DEPS = $(XBUILD_GEN_SYMTAB)
+
+# $(call xbuild_gen_symtab)
+define xbuild_gen_symtab
+	$(call xbuild_action,GEN,$@) \
+		$(NM) -S -n $< | $(XBUILD_GEN_SYMTAB) > $@
+endef
+
 define xbuild_clean
-	$(Q)rm -f x15 \
-	$(x15_OBJDEPS) \
-	$(x15_OBJECTS) \
+	$(Q)rm -f x15 $(x15_NO_SYMTAB) \
+	$(x15_OBJDEPS) $(x15_OBJECTS) \
+	$(x15_SYMTAB_C) $(x15_SYMTAB_D) $(x15_SYMTAB_O) \
 	$(x15_LDS)
 endef
 
@@ -225,6 +234,7 @@ TOOLCHAIN_PREFIX = $(TOOLCHAIN_NAME)-
 endif
 
 CPP := $(CC) -E
+NM  := $(TOOLCHAIN_PREFIX)nm
 
 CFLAGS ?= -O2 -g
 
@@ -297,9 +307,13 @@ COMPILE := $(CC) $(XBUILD_CPPFLAGS) $(XBUILD_CFLAGS)
 
 # Don't change preprocessor and compiler flags from this point
 
+x15_NO_SYMTAB := .x15.no_symtab
 x15_SOURCES := $(x15_SOURCES-y)
 x15_OBJDEPS := $(call xbuild_replace_source_suffix,d,$(x15_SOURCES))
 x15_OBJECTS := $(call xbuild_replace_source_suffix,o,$(x15_SOURCES))
+x15_SYMTAB_C := .symtab.c
+x15_SYMTAB_D := $(call xbuild_replace_source_suffix,d,$(x15_SYMTAB_C))
+x15_SYMTAB_O := $(call xbuild_replace_source_suffix,o,$(x15_SYMTAB_C))
 x15_LDS := $(basename $(x15_LDS_S))
 x15_LDS_D := $(x15_LDS).d
 
@@ -331,9 +345,23 @@ x15_DEPS := $(x15_LDS) .x15.sorted_init_ops
 %.lds: %.lds.S include/generated/autoconf.h
 	$(xbuild_gen_linker_script)
 
-x15: $(x15_OBJECTS) $(x15_DEPS)
+ifeq ($(CONFIG_SYMTAB),y)
+x15_FIRST_PASS := $(x15_NO_SYMTAB)
+else
+x15_FIRST_PASS := x15
+endif
+
+$(x15_FIRST_PASS): $(x15_OBJECTS) $(x15_DEPS)
 	$(call xbuild_link,$(x15_OBJECTS))
 
+ifeq ($(CONFIG_SYMTAB),y)
+$(x15_SYMTAB_C): $(x15_FIRST_PASS) $(XBUILD_GEN_SYMTAB_DEPS)
+	$(call xbuild_gen_symtab)
+
+x15: $(x15_NO_SYMTAB) $(x15_SYMTAB_O)
+	$(call xbuild_link,$(x15_OBJECTS) $(x15_SYMTAB_O))
+endif
+
 .PHONY: install-x15
 install-x15:
 	install -D -m 644 x15 $(DESTDIR)/boot/x15
diff --git a/kern/Makefile b/kern/Makefile
index 5b04fcb3..ea7e3bff 100644
--- a/kern/Makefile
+++ b/kern/Makefile
@@ -29,6 +29,7 @@ x15_SOURCES-y += \
         kern/spinlock.c \
         kern/sref.c \
         kern/string.c \
+        kern/symbol.c \
         kern/syscnt.c \
         kern/task.c \
         kern/thread.c \
diff --git a/kern/symbol.c b/kern/symbol.c
new file mode 100644
index 00000000..30df091e
--- /dev/null
+++ b/kern/symbol.c
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2018 Agustina Arzille.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <kern/macros.h>
+#include <kern/symbol.h>
+
+const size_t symbol_table_size __weak;
+const struct symbol *symbol_table_ptr __weak;
+
+const struct symbol *
+symbol_lookup(uintptr_t addr)
+{
+    const struct symbol *symbol;
+    uintptr_t start, end;
+
+    for (size_t i = 0; i < symbol_table_size; i++) {
+        symbol = &symbol_table_ptr[i];
+
+        if (!symbol->name || (symbol->size == 0)) {
+            continue;
+        }
+
+        start = symbol->addr;
+        end = symbol->addr + symbol->size;
+
+        if ((addr >= start) && (addr < end)) {
+            return symbol;
+        }
+    }
+
+    return NULL;
+}
diff --git a/kern/symbol.h b/kern/symbol.h
new file mode 100644
index 00000000..61fbf3f0
--- /dev/null
+++ b/kern/symbol.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2018 Agustina Arzille.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef KERN_SYMBOL_H
+#define KERN_SYMBOL_H
+
+#include <stdint.h>
+
+#include <kern/macros.h>
+
+#define __symbol_table __section(".symbol")
+
+/*
+ * Symbol structure.
+ *
+ * This structure is public.
+ */
+struct symbol {
+    uintptr_t addr;
+    uintptr_t size;
+    const char *name;
+};
+
+/*
+ * Look up a symbol from an address.
+ *
+ * NULL is returned if no symbol was found for the given address.
+ */
+const struct symbol * symbol_lookup(uintptr_t addr);
+
+#endif /* KERN_SYMBOL_H */
diff --git a/tools/gen_symtab.py b/tools/gen_symtab.py
new file mode 100755
index 00000000..b691da12
--- /dev/null
+++ b/tools/gen_symtab.py
@@ -0,0 +1,30 @@
+#!/usr/bin/env python3
+'''
+Embedded symbol table generator.
+'''
+
+import sys
+
+symtab_size = 0
+symtab = []
+
+for line in sys.stdin:
+    line = line.strip()
+    parts = line.split(' ')
+    del parts[2]
+
+    if len(parts) != 3 or parts[2].startswith("__func__."):
+        continue
+
+    symtab.append("{ 0x%s, 0x%s, \"%s\" }" % tuple(parts))
+    symtab_size += 1
+
+print("#include <kern/symbol.h>")
+print("const struct symbol symbol_table[] __symbol_table = {")
+
+for elem in symtab:
+    print("    " + elem + ",",)
+
+print("};")
+print("const size_t symbol_table_size = %d;" % symtab_size)
+print("const struct symbol *symbol_table_ptr = symbol_table;")